Support is requested for a study of human temporal bone histopathology to focus on 1) congenital abnormalities of the temporal bone, 2) endolymphatic hydrops, 3) sudden deafness and/or sudden hearing loss, 4) facial paralysis, and 5) other clinically significant temporal bone abnormalities. In addition, we will study the microscopic anatomy of clinically important areas of the human temporal bone, in particular the vascular system in the vestibular aqueduct and the perineural sheath of the facial nerve in the facial canal. There is a great need to increase our knowledge in all of these areas. Knowledge acquired from this study will establish the anatomical pathology necessary for a better understanding of clinical problems and better patient care, in otology, audiology, genetics, meurology, oncology, pediatrics, vestibulology, and virology. The human temporal bones are processed for sectioning serially in celloidin-embedded blocks. Every tenth section is stained with hematoxylin and eosin and carefully examined. We now have 1,499 human temporal bones from 887 interesting cases which are either available for study or being processed in our laboratory. These bones have been and will be available in providing new information about the anatomy and pathology of the human ear; however, in order to expand our knowledge of the human temporal bone it is essential that we continue to collect and to examine new specimens and to study new areas of interest. Without increasing our small store of knowledge of temporal bone anatomical pathology we cannot hope to further our understanding of the pathophysiology of ear disease. Just as advances in the care of the cardiac patient are based on new discoveries about cardiac function which grow out of basic research in this area, so we must continually seek to understand better the basic function of the ear so that clinical problems with their organ may some day be resolved. Congenital deafness, Meniere's disease, sudden deafness, facial paralysis - each of these serious handicaps may result from any one of many different pathological processes. Classically, an understanding of anatomical pathology is the essential first step in determining the fundamental causes of such disorders.